A liquid crystal display (LCD, being an non-active light emitting device, usually is designed to operate in conjunction with a backlight module for achieving a stable brightness and good color performance, whereas pixels in an image of various grey levels or brightness values can be achieved through the control of the driving circuits and the liquid crystal layer in the LCD, and the color presentation of each pixel can be achieved through the red-photoresist coating, green-photoresist coating and blue-photoresist coating in its color filter. However, if the panel of a display device is defected, there can be abnormality to the color presentation happening in some pixels of the display device, i.e. there can be hot pixels or dark pixels existed in the panel. Among which, since the hot pixels clearly stand out above the rest, the amount of hot pixels existed can treated as an essential element for ranking display panels.
There are already many studies focusing on technique for repairing LCD. One of which is a method for repairing LCD panel, disclosed in TW Pat. Pub. No. 200827819, in which, first, a beam of nanosecond laser is projected on the filter of a LCD panel for producing gaps on the filter, and then a beam of femtosecond laser or diode laser is projected on the filter while enabling the same to be linearly absorbed by the filter with gaps, and thus altering the physical characteristic of the filter so as to reduce the transmittance relating to the hot pixels of the LCD panels. It is noted that in the aforesaid study, a single photo linear absorption is observed on the filter under the projection of the femtosecond laser. Another such study is a method and apparatus for repairing LCD panel, disclosed in TW Pat. Pub. No. 200829977, in which according to the linear absorption characteristic of the LCD panel, the repair can be performed using a continuous-wave (CW) laser with a wavelength ranged between 400 nm to 490 nm, a pulse laser, or a femtosecond laser with a wavelength of 450 nm and a frequency higher than 10 MHz. However, the aforesaid laser projection should be performed through the transistor side of the LCD since the laser projection can easily cause damage to the polarizer in the LCD if it is projected from the color filter side. Nevertheless, since the transmittances of the laser whose wavelength is ranged between 400 nm to 490 nm are low with respect to the red-photoresist coating and green-photoresist coating as well, the hot pixels of the LCD panel will be subjected to band processed by beams of suitable energy.
Moreover, in WO 2008-156286, a repairing method capable of effectively repairing a bright pixel defect of a display device using laser is disclosed, in which as the display device is configured with black matrices, the method includes forming a gap at a color filter having a bright pixel defect between the color filter and a glass using laser, and decomposing black matrices neighboring to the color filter using laser for diffusing the gaps with the melt black matrices so as to blacken the photoresist of the deflective pixels. In addition, in another repairing method disclosed in U.S. Pat. No. 7,502,094, the surface of the color filter in a LCD panel that is facing toward its substrate is blackened by projecting a Nd:YAG laser of 380˜740 in wavelength and of a frequency higher than 55 Hz upon the surface. As there can be diffusion during the laser projection, three optical masks of different sizes are used for minimizing the diffusion effect so as to enhance the not pixel repairing efficiency.
In an apparatus and method for repairing liquid crystal display device disclosed in U.S. Pat. No. 7,636,148, there are three different repairing methods being provided. The three repairing methods all includes the steps of: forming a repairing film on any one of a first substrate and a second substrate; sensing a defect area in the liquid crystal display panel; and irradiating a laser, such as an excimer laser, a diode laser or a Nd:YAG laser, to an area of the repairing film corresponding to the defect area, but the different is that: the repairing film in the first method is a transparent organic film, the repairing film in the second method is a black matrix; and the repairing film in the third method is a pattern spacer. Moreover, in a method for the correction of a defect in a liquid crystal display device disclosed in U.S. Pat. No. 5,926,246, an aligning film in a defective pixel is irradiated with a laser to form minute grooves in a different direction than the rubbing direction of the aligning film, whereby the orientation of the liquid crystal is changed so that the liquid crystal between the aligning films is no longer twisted. Thereby, a defective pixel present in a liquid crystal display panel can be made inconspicuous, and as a result, degradation of the display quality of the liquid crystal display device after correction can be prevented. It is noted that for preventing other areas in the LCD device from being damaged by the laser projection, the wavelength of the laser is ranged between 200 nm to 450 nm. In the aforesaid patent, by the projection of the laser upon the aligning film, the liquid crystal molecules in the liquid crystal layer of the defective pixel are oriented randomly at the irradiation spots. Therefore, the spots irradiated by laser beams on the defective pixel allow light of an intermediate tone to transmit therethrough, whereas the amount of transmitted light can be regulated in the areas surrounding the laser beam irradiated spots. Accordingly, the defective pixel present in the liquid crystal display panel, as a whole, can be made inconspicuous, and as a result, a decline in the display quality of the liquid crystal display device after correction can be prevented.